how to write letter in English,pls tell me some details.I wi

how to write letter in English,pls tell me some details.I will add more score to express my gratitude.

（一）开 头 段：
1、告知对方你的身份（假如对方不认识你）
Dear Sir/Mr.Prometheus,
I was a student at your college,enrolled in Philosophy Department.
/ I am a … at your …
/ I am a … at your college,enrolled in the … course.
/ My name is …,I am ….
2、问候收信人（假如他/她是你的朋友）
Dear Prometheus,
Hello/Hi.How are you?/ I hope everything is fine./ How are things going with you?
/ How are you getting on in……?
3、解释写信的原因
（1）致谢：
I deeply appreciate your courtesy and I hope to reciprocate your favor when the opportunity arises.
/ I am greatly indebted to you for (the double) you have gone to on my behalf.
/ Thank you for your letter about studying in Canada.
/ I am writing to you to express my heartfelt gratitude.
/ I am writing to tell you how grateful I am for…….
/ I would like to thank you most sincerely for…….
（2）抱怨：
I am writing to complain about the poor service at your dining-room.
/ I am writing to express my dissatisfaction with/at …
/ I wish to make a complaint about…….
/ I am writing to draw your attention to…….
/ I am afraid I have got a complaint about…….
（3） 致歉：
I would be grateful if you would be so kind as to provide me with certain essential information regarding the following aspects.
/ I am writing to you because I am unable to…….
/ I am terribly sorry that…….
/ I would like to express my apologies for not being able to…….
（4）询问：
I would like to obtain/request/seek/inquire about some information about…
/ I am writing to ask if you can do me a favor.
/ I would like some detailed information on/about……
（二） 结 尾 段：
1、发出请求
（1） Please give this matter your immediate attention.
（2）I would very much appreciate it if……as soon as possible.
（3）Please render me some valuable advice which is conducive to my final decision.
2、提供帮助
（1）I hope these ……will be helpful,and please feel free to contact me for more information.
（2）……will be taking over responsibility for you and if you should need any assistance,she/he will be pleased to help you.
3、再次表示歉意或感激
（1）Thank you for your kind assistance.
（2）Please accept my heartfelt thanks and deepest gratitude,now and always.
（3）I am sorry that I cannot……,and trust that you will understand.
（4）In addition,let me apologize for any inconvenience I may have caused.
（5）I shall feel obliged by a reply at your earliest convenience.
（6）Once again,I am sorry for any inconvenience caused.
4、期盼回信
（1）I look forward to your prompt response.
（2）Looking forward to a prompt reply.
（3）I expect to hear from you very soon.
（4）I hope to receive your reply shortly.
（5）I am already eagerly awaiting your reply to this first letter.